TM 9--2815--247--34 0004 00--3 THEORY OF OPERATION -- CONTINUED 0004 00 CYLINDERS AND VALVES -- CONTINUED A camshaft bearing surface is provided in each cylinder. The camshaft bearing is bored with the cylinder head valve rocker support cover in place; therefore, the covers are not interchangeable and each must remain as a part of a specific cylinder assembly. Each cylinder has replaceable camshaft bearings at the camshaft bore. Identifying numbers are used on cylinder and covers to prevent mismatching. Counter bores in the rocker box and rocker support covers accommodate the inter--cylinder rubber hoses and the steel flanges which enclose the camshaft between the cylinders. The stem of the intake valve (48) and exhaust valve (47) for each cylinder extends into the rocker box. Three nested springs, compressed between two retainers and secured to the valve stem by two cone--shaped locks, hold each valve to its seat. Each exhaust valve has a positive valve rotator which also serves as the lower spring re- tainer. Valve clearance adjusting screws with flat swivel pusher pads are mounted on one end of the valve rocker arms (1 and 2). Forged steel valve rocker arms (1 and 2) with roller cam--followers are used. The rollers are hardened and honed to provide an extremely smooth and permanent contact surface. Hollow rocker arm shafts and drilled passages in the rocker arms convey oil to all moving parts. CAMSHAFTS NOTE The key numbers shown in parentheses refer to Figure 1--6. The left and right camshaft assemblies (3 and 10) are mounted, one on each bank, on the cylinders and operate the valve mechanism. The camshafts are hollow to provide oil passages for pressure lubrication to the valve parts and to permit deflection when the cylinders fire. Tubular molded rubber hoses enclose the camshafts between cyl- inders. Each camshaft is driven by the accessory drive gear (12), accessory drive gearshaft assembly (8), camshaft drive bevel gearshaft (7), camshaft drive gearshaft (5), and camshaft driven gear (4) through an inclined quill type cam- shaft drive shaft (6). The drive shafts can be removed to permit separate rotation of the camshafts for engine tim- ing. When camshafts are correctly positioned in relation to the crankshaft, the drive shafts have different number of splines on each end and this allows them to be inserted in the camshaft bevel gearshafts without disturbing rela- tionship between camshafts and crankshaft. LUBRICATION SYSTEM NOTE Refer to Figures 1--7 and 1--8 while reading the following information. General  The main pressure oil pump draws oil from the pressure oil pump compartment in the oil pan. This compartment is fed by the scavenge oil pump which picks up oil from the front end of the oil pan and by oil which drains into the pressure compartment from the cover of the pressure pump compartment and the reserve compart- ment. The pressurized oil is forced through the engine oil coolers and oil filter to the engine oil galleries, bearings, turbosuperchargers, fuel injection pump and to the piston oil sprayer nozzles. These nozzles are located in the crankcase below each cylinder and provide a continuous oil spray to the pistons and cylinder walls.